(a) Field of the Invention
The present invention relates to a liquid crystal display and, more particularly, to a liquid crystal display which has a wide viewing angle.
(b) Description of the Related Art
Generally, liquid crystal displays have a structure where a liquid crystal is sandwiched between two substrates, and the electric field applied to the liquid crystal changes its arrangement to control light transmission.
Among them, the vertically aligned twisted nematic (VATN) liquid crystal displays have a pair of internal transparent substrates with transparent electrodes, a liquid crystal sandwiched between the substrates, and two polarizing plates externally attached to the substrates one by one. The liquid crystal molecules are initially aligned perpendicular to the substrates and, under the application of an electric field, they are spirally twisted with a predetermined pitch while being oriented to be parallel to the substrates.
When the polarizing plates are normal to each other in the polarizing direction, light is completely blocked when there is no application of an electric field. That is, in the so-called normally black mode, brightness is very low at an off state and hence the contrast ratio is high compared to the usual TN liquid crystal display. However, under the application of voltage (particularly gray scale voltage), a significant difference is present in retardation of light depending upon the viewing directions as in the usual TN liquid crystal display, so that the viewing angle becomes too narrow.
In order to solve such a problem, it has been proposed that the electrodes be patterned to generate fringe fields, and that the fringe fields generate several micro-regions with different orientation directions of the liquid crystal molecules. For instance, U.S. Pat. No. 5,309,264 issued to Lien discloses a technique of forming X-shaped opening portions at the common electrode. U.S. Pat. No. 5,434,690 issued to Histake et al. discloses a technique of forming opening portions at the electrodes of the top and bottom substrates in an alternate manner.
However, the above techniques require a separate mask to pattern the common electrode. Furthermore, since the color filter pigments may influence the liquid crystal, a protective layer must be formed on the color filters. It also generates serious textures at the periphery of the patterned electrodes.
It is an object of the present invention to provide a liquid crystal display which has a wide viewing angle with improved picture quality.
This and other objects may be achieved by a liquid crystal display having a color filter substrate and a thin film transistor array substrate.
The color filter substrate is overlaid with color filters with depression patterns, and a black matrix surrounding the color filters. A common electrode is formed on the color filters with the depression patterns to make partitioned orientations of the liquid crystal molecules.
The black matrix may be overlapped with the depression patterns of the color filters to reduce the light leakage.
The thin film transistor array substrate faces the color filter substrate with pixel electrodes. The pixel electrodes are provided with opening patterns. When the opening patterns of the pixel electrodes, and the depression patterns of the color filters proceed parallel to each in an alternate manner, stable orientations of the liquid crystal molecules and a wide viewing angle can be obtained.
When the common electrode is formed by depositing thin indium tin oxide onto the substrate twice, the common electrode at the periphery of the depression patterns can be prevented from being cut.
Furthermore, the common electrode also has depression patterns corresponding to those of the color filters, with the angle of the side wall of the depression pattern of the common electrode being 30-120xc2x0 with respect to the thin film transistor array substrate.
Storage capacitor electrodes are further formed at the thin film transistor array substrate. When viewed from the top side, the pixel electrodes completely cover the storage capacitor electrodes at a predetermined region.